This invention relates to display lamps. More particularly, it relates to low voltage display lamps having a heat-reducing heat shield with an optically curved surface.
Low voltage display lamps are known in the art. Low voltage display lamps for use in standard lamp sockets having line-voltage, such as, e.g., the well known MR16 lamps, comprise a reflector assembly that works in conjunction with a voltage converter such as solid state electronic ballast. The ballast is contained within a lamp housing together with, disposed in close proximity to and directly behind the reflector assembly. Consequently, it is important to minimize radiant heat from the reflector assembly to the ballast in order to ensure proper operation and a long service life.
Current display lamp designs employ a flat circular heat shield or plate which is disposed behind the elliptical reflector of the reflector assembly and in front of the ballast. This heat shield serves to protect the ballast by reflecting infrared radiation (IR) generated by the filament and transmitted through the reflector, thereby reducing the ballast""s operating temperature. However, a significant portion of the reflected IR is directed at the interior surface of the lamp housing. Consequently, the lamp housing, which is already subject to direct IR energy from the filament, now absorbs roughly twice the IR compared to that radiated directly from the filament to the housing.
The result is that the housing is more susceptible to melting from absorbed IR, and also that the absorbed IR will be conducted as heat through the housing material to the ballast, thereby raising the ballast operating temperature and shortening its service life.
Existing means for solving the problem of ballast heating include multi-layer coatings applied to the concave reflector surface that are designed to reflect IR instead of transmit it through the reflector toward the ballast. However, such coatings are difficult to design and apply correctly and often are very expensive. Most such coatings involve applying a discrete coating layer separate from the reflective coating layer, thereby contributing an additional coating process. It has been further suggested that a broad-band dichroic coating that would reflect in both the visible and IR spectra could be used, however such a coating would be difficult to apply correctly, and could adversely affect the lumen efficiency of the lamp.
There is a need in the art for a low voltage display lamp, for use in standard line-voltage electric lamp sockets, comprising an efficient heat shield that effectively reflects IR away from the ballast, and also that does not direct such reflected IR energy toward the lamp housing. Preferably, such a heat shield will reflect IR energy back through the lamp reflector to exit the lamp through the lamp cover. Such a heat shield will effectively reduce the ballast operating temperature.
A low voltage display lamp is provided having a lamp housing, a reflector assembly, a solid state electronic ballast, and a heat shield. The reflector assembly has a light source and is located within the housing, with the ballast located behind the reflector assembly. The heat shield is located between the ballast and the reflector assembly, and has an optically curved surface.